(a) Field
The present disclosure relates to mounting units for vehicle sub-frames.
(b) Description of the Related Art
In general, a front sub-frame (hereinafter, simply referred to as a sub-frame) of a vehicle mounts power train parts such as an engine and a transmission in a monocoque vehicle body structure.
FIG. 1 illustrates a perspective view of an assembly between a common side member and a sub-frame.
As shown in the example of FIG. 1, a sub-frame 101 is combined with a lower part of a front side member (hereinafter, simply referred to as a side member) 103 on both sides of a vehicle body through a mounting unit, as will be discussed below in reference to FIGS. 2 and 3.
As the sub-frame 101 is used for mounting and supporting power trains of a vehicle, a large load is continuously applied to the sub-frame 101 during the operation of the vehicle (e.g., while the vehicle is driven). Accordingly, the mounting unit must connect the side member 103 of the vehicle body to the sub-frame 101 so that they are firmly combined with each other.
FIG. 2 shows an exploded perspective view of an assembly unit of a side member to which a conventional mounting unit is applied. FIG. 3 is a perspective view of an assembly unit of a side member to which a conventional mounting unit is applied.
In particular, FIGS. 2 and 3 illustrate an exemplary mounting unit 100 for engaging the sub-frame 101 with the side member 103 of FIG. 1. As shown in FIG. 2, the mounting unit 100 may be assembled by connecting a supporting end 111 of a mounting nut 110 with a bracket 120. In this example, a head 113 of the mounting nut 110 may then be welded to the side member 103 after the head 113 is inserted into a through hole H formed in a lower surface of the side member 103.
For example, the mounting nut 110 may be assembled with the bracket 120 and the side member 103 by arc welding or combined with the bracket 120 and the side member 103 by spot welding.
The range of motion of the mounting unit 100 must be restricted in order to suppress any excessive movement that would prevent the side member 103 from being firmly combined with the sub-frame 101. The mounting unit 100 has the following supporting structure.
In this example, the supporting structure of the mounting unit 100 includes a circular supporting end 111 in a central portion of the mounting nut 110 for combining the mounting nut 110 with the bracket 120. The head 113 of the mounting nut 110 and a periphery of the through hole H of the side member 103 are also combined with each other so that the degree of freedom of motion of the mounting nut 110 is suppressed.
The degree of freedom of motion of the mounting unit 110 is further suppressed by increasing the amount of stiffness between the bracket 120 and the side member 103, as they are combined with the mounting nut 110.
In such a supporting structure, a greater amount of stiffness may be required, as numerous vehicle body parts must be installed around a single joint of the mounting unit 100. Accordingly, the amount of stiffness may be increased by applying an additional reinforcing member 130, as shown in FIG. 2.
Vertical stiffness around the joint of the mounting unit 100 may be secured by applying the reinforcing member 130. However, there may be various limitations on increasing stiffness to suppress movement in a horizontal direction, also referred to herein as back and forth or side to side supporting stiffness.
In particular, as shown in FIG. 1, a fender upper connecting member 140 may be installed so as to be connected to a vehicle body fender in a periphery of the side member 103 in which the mounting unit 100 is provided. This requires additional back and forth and side to side supporting stiffness for the periphery of the side member 103.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may include information that may not considered prior art that would have been known to a person of ordinary skill in the relevant art.